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Players from the Santa Monica Vikings Mitey Mites and Jr. Pee Wees came home after they had become violently ill while at the National Youth Football Championships in Las Vegas. Thirteen children and five adults were hospitalized Friday, and the illness affected dozens of others. Jane Yamamoto reports for the NBC4 News at 9 p.m. Sunday, Dec. 1, 2013. (Published Sunday, Dec 1, 2013)

A Santa Monica youth football team returned home Sunday after 40 people affiliated with the team developed severe flu-like symptoms such as vomiting, cramping and diarrhea while at a tournament in Las Vegas.

Thirteen children and five adults were hospitalized Friday, and the illness has affected 58 children and 29 adults on at least nine teams attending the National Youth Football Championships.

More than half the players from the Santa Monica Vikings Mitey Mites and Jr. Pee Wees became violently ill before the championships.

A 10-year-old running back who was among nearly a dozen players who had to be hospitalized said everyone was vomiting and could barely walk.

"At the hospital, they gave us pills to take that stopped me from throwing up," he said.

The cause of the illness has yet to be determined, but health officials say the outbreak could be due to norovirus, a mostly food or waterborne illness that can also spread by an infected person.

"They are saying it is very likely that a player who was sick at home and came to Las Vegas on a bus likely was the cause, and it spread to that team and then to other teams," tournament spokesman Justin Gates told NBC-affiliate KNSV.

Health officials have taken stool samples to determine whether norovirus is the cause for outbreak. In the meantime, they are encouraging those affected to wash their hands properly and take the necessary measures to ensure the sickness doesn’t spread.

Norovirus causes inflammation to the stomach, intestines or both, leading to stomach pain, nausea, diarrhea and vomiting, according to the Center for Disease Control and Prevention.